An end-piece for an additive guide tube is disclosed. Such an end piece may have a durable sleeve and a sloughable sleeve. The sloughable sleeve may have a channel through which an additive may be delivered, and the sloughable sleeve may reside in the through-hole of the durable sleeve and may be secured to the durable sleeve. When molten metal contacts the sloughable sleeve, the sloughable sleeve burns or melts and sloughs off, thereby preventing the molten metal and slag from sticking to the end-piece, which in turn prevents buildup of metal and slag.